It is common practice to affix printed posters, calendars and the like to a flat, vertical surface, e.g, a wall. The purposes for doing so are wide and varied. For example, there is the college student who wants to decorate his or her dorm walls but cannot afford framed pictures and is prohibited by school authorities from mounting any materials requiring nails to be imbedded in the walls. Like most students, this student will choose to decorate his or her dorm walls by affixing unframed printed posters with tape, tacks, or other adhesive materials.
Several products are available in the art for affixing printed material to a vertical surface. Among the most common are tacks, adhesive tape, double-sided adhesive strips, or other adhesive materials, and paper that is manufactured with an adhesive on one side. These products have their individual disadvantages. Tacks will cause damage, although minimal, to the surface being affixed to. Although the tiny holes formed by imbedding a tack into a wall or other penetrable surface are necessary to the use of a tack, however, they may blemish the surface's appearance when the tacks are later removed and not replaced or subsequently covered. Adhesive tape, strips and the like are also disadvantageous. Some have a tendency to lose their adhesive quality after extended use. Others, although maintaining their adhesiveness, are difficult to remove from a surface. This can cause paint to lift or paneling to be tarnished when the adhesive material is removed. Another disadvantage of such products is that they can be used only once--their adhesive capability is lost once they are removed from a surface.
An alternative product known in the prior art is a polymer electret film, or in other terms, an electrostatically-charged plastic film. The electrostatically-charged film "sticks" to a vertical surface by means of the electrostatic charge created between the paper and the surface. An advantage of this product over the conventional methods discussed is the ability to be affixed and removed from a vertical surface more than once. In fact, the "adhesive" ability will last as long as the film remains electrostatically charged and clean. Additionally, unlike a tack or adhesive, there is no risk of damaging or blemishing walls and other surfaces.
The best process for the printing of posters on uncharged polymer film uses ultraviolet-curable inks which are applied using offset printing techniques commonly known in the art. The printed polymer film is then heated in order to accelerate the drying process. Electret film is not suitable for these printing processes known in the art. The heating process discharges or significantly reduces the electric charge of the film.
Accordingly, it is the main object of the present invention to provide an improved apparatus and method for generating posters which improves upon the prior art.
A further object of the present invention is to provide an apparatus and method for generating posters which are electrostatically charged.